fix(mobile): use shared auth for background_downloader (#26911)

shared client for background_downloader on ios

mobile/android/app/src/main/kotlin/app/alextran/immich/core/HttpClientManager.kt

@@ -27,7 +27,11 @@ import kotlinx.serialization.Serializable
 import kotlinx.serialization.json.Json
 import java.io.ByteArrayInputStream
 import java.io.File
+import java.net.Authenticator
+import java.net.CookieHandler
+import java.net.PasswordAuthentication
 import java.net.Socket
+import java.net.URI
 import java.security.KeyStore
 import java.security.Principal
 import java.security.PrivateKey
@@ -104,6 +108,25 @@ object HttpClientManager {
       keyChainAlias = prefs.getString(PREFS_CERT_ALIAS, null)
 
       cookieJar.init(prefs)
+      System.setProperty("http.agent", USER_AGENT)
+      Authenticator.setDefault(object : Authenticator() {
+        override fun getPasswordAuthentication(): PasswordAuthentication? {
+          val url = requestingURL ?: return null
+          if (url.userInfo.isNullOrEmpty()) return null
+          val parts = url.userInfo.split(":", limit = 2)
+          return PasswordAuthentication(parts[0], parts.getOrElse(1) { "" }.toCharArray())
+        }
+      })
+      CookieHandler.setDefault(object : CookieHandler() {
+        override fun get(uri: URI, requestHeaders: Map<String, List<String>>): Map<String, List<String>> {
+          val httpUrl = uri.toString().toHttpUrlOrNull() ?: return emptyMap()
+          val cookies = cookieJar.loadForRequest(httpUrl)
+          if (cookies.isEmpty()) return emptyMap()
+          return mapOf("Cookie" to listOf(cookies.joinToString("; ") { "${it.name}=${it.value}" }))
+        }
+
+        override fun put(uri: URI, responseHeaders: Map<String, List<String>>) {}
+      })
 
       val savedHeaders = prefs.getString(PREFS_HEADERS, null)
       if (savedHeaders != null) {

mobile/ios/Runner/AppDelegate.swift

@@ -20,6 +20,7 @@ import UIKit
     }
 
     SwiftNativeVideoPlayerPlugin.cookieStorage = URLSessionManager.cookieStorage
+    URLSessionManager.patchBackgroundDownloader()
     GeneratedPluginRegistrant.register(with: self)
     let controller: FlutterViewController = window?.rootViewController as! FlutterViewController
     AppDelegate.registerPlugins(with: controller.engine, controller: controller)

mobile/ios/Runner/Core/URLSessionManager.swift

@@ -51,7 +51,7 @@ class URLSessionManager: NSObject {
     diskCapacity: 1024 * 1024 * 1024,
     directory: cacheDir
   )
-  private static let userAgent: String = {
+  static let userAgent: String = {
     let version = Bundle.main.object(forInfoDictionaryKey: "CFBundleShortVersionString") as? String ?? "unknown"
     return "Immich_iOS_\(version)"
   }()
@@ -158,6 +158,49 @@ class URLSessionManager: NSObject {
 
     return URLSession(configuration: config, delegate: delegate, delegateQueue: nil)
   }
+
+  /// Patches background_downloader's URLSession to use shared auth configuration.
+  /// Must be called before background_downloader creates its session (i.e. early in app startup).
+  static func patchBackgroundDownloader() {
+    // Swizzle URLSessionConfiguration.background(withIdentifier:) to inject shared config
+    let originalSel = NSSelectorFromString("backgroundSessionConfigurationWithIdentifier:")
+    let swizzledSel = #selector(URLSessionConfiguration.immich_background(withIdentifier:))
+    if let original = class_getClassMethod(URLSessionConfiguration.self, originalSel),
+       let swizzled = class_getClassMethod(URLSessionConfiguration.self, swizzledSel) {
+      method_exchangeImplementations(original, swizzled)
+    }
+
+    // Add auth challenge handling to background_downloader's UrlSessionDelegate
+    guard let targetClass = NSClassFromString("background_downloader.UrlSessionDelegate") else { return }
+
+    let sessionBlock: @convention(block) (AnyObject, URLSession, URLAuthenticationChallenge,
+        @escaping (URLSession.AuthChallengeDisposition, URLCredential?) -> Void) -> Void
+    = { _, session, challenge, completion in
+      URLSessionManager.shared.delegate.handleChallenge(session, challenge, completion)
+    }
+    class_replaceMethod(targetClass,
+      NSSelectorFromString("URLSession:didReceiveChallenge:completionHandler:"),
+      imp_implementationWithBlock(sessionBlock), "v@:@@@?")
+
+    let taskBlock: @convention(block) (AnyObject, URLSession, URLSessionTask, URLAuthenticationChallenge,
+        @escaping (URLSession.AuthChallengeDisposition, URLCredential?) -> Void) -> Void
+    = { _, session, task, challenge, completion in
+      URLSessionManager.shared.delegate.handleChallenge(session, challenge, completion, task: task)
+    }
+    class_replaceMethod(targetClass,
+      NSSelectorFromString("URLSession:task:didReceiveChallenge:completionHandler:"),
+      imp_implementationWithBlock(taskBlock), "v@:@@@@?")
+  }
+}
+
+private extension URLSessionConfiguration {
+  @objc dynamic class func immich_background(withIdentifier id: String) -> URLSessionConfiguration {
+    // After swizzle, this calls the original implementation
+    let config = immich_background(withIdentifier: id)
+    config.httpCookieStorage = URLSessionManager.cookieStorage
+    config.httpAdditionalHeaders = ["User-Agent": URLSessionManager.userAgent]
+    return config
+  }
 }
 
 class URLSessionManagerDelegate: NSObject, URLSessionTaskDelegate, URLSessionWebSocketDelegate {